Radiation detectors are needed today for both safety and security applications. For safety applications, a personal radiation detector may be needed to monitor both the rate of radiation exposure and a total dose. For example, a portable rate meter can monitor a subject's exposure to radiation and provide a warning if the rate of radiation exposure reaches an unacceptable level, and a portable dosimeter can measure the accumulated radiation exposure that a subject receives during a period of time. Traditionally, implementations of dose rate meters and dosimeters have differed significantly. For example, one class of rate meters employs Geiger-Müller tubes to detect or count the rate at which ionizing radiation passes into the Geiger-Müller tube. In contrast, dosimeters can be implemented simply be carrying film in a light-tight package and developing the film to measure the amount of radiation that has penetrated the packaging and exposed the film.
Radiation measurements for security purposes confront a different set of demands and concerns. For example, detecting a source of radiation, which may pose a security threat, generally requires the ability to sense relatively low levels of radiation because the device containing radioactive material may be hidden, shielded, or separated from the detector. As a result, the rate of radiation reaching a detector from such security threats may be low when compared to the rates consider unacceptable for personal safety. Radiation detectors for security applications thus may need to be orders of magnitude more sensitive than a personal radiation rate meters suitable for safety applications
The differences in requirements for personal radiation rate meters and portable radiation detectors for security have led to adoption of separate standards for such detectors. For example, recent actions to improve homeland security have led to development of ANSI standard N42.32 for alarming personal radiation detectors and ANSI standard N42.33 for portable radiation detectors for security applications. However, in many situations, security personnel or others will want to have a personal radiation dosimeter and a safety alarm in addition to a portable radiation detector for detection of security threats. The need to purchase and carry two types of radiation detectors can be costly and cumbersome.